You need more data. Just because 72% of apartments are under rent control doesn't mean that 72% of apartments are going for under market rate rent.
Even with rent control, San Francisco would benefit from being denser. There's a lack of all kinds of housing which is making it unaffordable. Manhattan is 70,000 people/mi2. Brooklyn is 35,000 people/mi2. SF is 17,000 people/mi2.
Even with rent control, San Francisco would benefit from being denser. There's a lack of all kinds of housing which is making it unaffordable. Manhattan is 70,000 people/mi2. Brooklyn is 35,000 people/mi2. SF is 17,000 people/mi2.